New Jerseyans should brace themselves for treacherously low temperatures on Friday night and Saturday, with the mercury plummeting below zero in northern sections of the state, according to the National Weather Service forecast.

In Lafayette, the overnight low will be 3 degrees below zero while West Milford may be slightly warmer: 2 degrees below zero.

“We’re talking about dangerous cold,” said David Robinson, the state climatologist at Rutgers University. “It’s going to be the type of cold where people have to be prepared. Keep a blanket in the car. It’s not like a normal cold day where you just put on a sweater and go to the store.”

Wind gusts of 20 mph could make it feel like 15 to 20 degrees below zero. Jim Bunker, a program leader with the National Weather Service in Mount Holly, said that people should wear layers, cover their faces and double up on gloves. Keep a half tank of gas in the car to ensure fuel lines don’t freeze. At home, run faucets to prevent pipes from freezing, Bunker said.

“Bring your pets in,” said Bunker. “Allow extra time for travel because there could be slick spots on the road with ice and snow. We issue wind chill advisories when the wind chill is 15-25 degrees below zero.”

Seek medical treatment but if the person cannot be taken to the doctor, they should be warmed up slowly.

Wrap the person in a blanket, warming their body core before their hands and feet. Warming extremities first flushes cold blood to the heart and can actually worsen hypothermia. Warm soup and food are healthier than hot beverages and alcohol, which lowers body temperature.

Saturday’s cold sting could shatter a record in Newark. Dating back to 1931, the lowest temperature on January 3 in the state’s largest city was 10 degrees, a record set in 1981.

Elsewhere in the state, record lows for the date were set during a 2001 cold snap. The record is 2 degrees in New Brunswick and 8 degrees below zero in Sussex Borough.

The lowest temperature on record in the Garden State is 34 degrees below zero, set in Rivervale on January 5 in 1904, according to Robinson.

Robinson said that the culprit for the frigid conditions on Friday and Saturday is the polar vortex, a core of cold air that normally swirls above Canada. The vortex will drop down south on Friday and Saturday, dragging down temperatures.

“This is not going to be like a 30 degree winter day,” said Robinson. “I know people don’t like wearing hats and gloves but if you’re going out, you need to be dressed for severe cold.”